Avoiding the spam folder

Spam-folder placement has more to do with sender reputation than email content — but content matters too. Here’s the prioritized list of what to actually fix.

The big four

1. Authenticate. SPF + DKIM + DMARC, all three, all aligned. 3AVA Mail provides the records — make sure they’re added correctly. Verify your domain.
2. Send to people who want it. Maintain list hygiene. Suppress hard bounces. Honor unsubscribes. Remove never-engaged contacts after 6 months. Audience hygiene →
3. Warm up gradually. New domains/IPs ramp; established ones stay consistent. Warming up →
4. Get engagement. Replies, clicks, “not spam” actions — all signal to providers that your mail is wanted. Provoke them by writing emails worth a reply, not just a click.

Content rules that matter

• Subject lines under 60 chars. Long subjects get truncated and look spammy.
• Don’t write subjects in ALL CAPS. Caps in subject lines correlate with spam.
• **Don’t use `

in subjects.** Same.

• Avoid trigger words in subjects only. “Free”, “guarantee”, “click here” in subjects raise scores. In body copy, they’re fine.
• Keep HTML clean. Inline styles, alt text on images, plain-text alternative. Don’t ship templates with broken or absent text parts.
• Plain text alternative is mandatory. A text field that’s not just stripped HTML — write it like a human.
• Single visible link to one CTA. Many links of varying domains is a spam signal.
• No URL shorteners. bit.ly, tinyurl, etc. are heavily flagged.
• Don’t attach big files. > 5MB attachments are suspicious.
• Image-to-text ratio matters. Mail that’s all image and no text is a spam-trap classic.

Headers that matter

• List-Unsubscribe with one-click — required by Gmail and Yahoo for bulk senders. 3AVA Mail adds this automatically for campaign sends.
• List-Unsubscribe-Post: List-Unsubscribe=One-Click — RFC 8058 one-click. 3AVA Mail adds this.
• Reply-To that points to a real human — not noreply@. Increases reply rate, which lifts reputation.
• Message-ID with your sending domain (not the SMTP relay’s). 3AVA Mail handles this.

What doesn’t matter as much as you think

• “Word count optimization” — there’s no magic number.
• Avoiding the word “free” in body copy.
• Using a noreply@ address (fine for transactional; bad for marketing).
• Whether you send from a subdomain or root — mostly equivalent if both are warmed properly. (Subdomain has a small edge — see Subdomain vs root.)

How to check your placement

• Postmaster Tools (Google) — set up at postmaster.google.com. Shows your reputation by IP and domain.
• SNDS (Microsoft) — register at sendersupport.olc.protection.outlook.com/snds/.
• mail-tester.com — for one-off tests; gives a 0–10 score with specific findings.
• inbox-placement test — services like GlockApps or Mail-Tester Premium test placement across 50+ inboxes.

If a campaign lands in spam at one provider but inbox at others, the issue is provider-specific (often Gmail-specific, since its filters are the strictest).

When everything’s “right” but mail still goes to spam

Almost always: insufficient engagement history. Providers want to see opens, clicks, replies, and “move to inbox” actions over time. The fix is to keep sending wanted mail consistently and let history accumulate. There’s no shortcut.